Menthol is well known for its physiological cooling effect on the skin and mucous membrances of the mouth and has been extensively used as a flavouring agent in tobacco for producing a "cool" sensation in the mouth when smoking.
It is well established that the "cooling" effect of menthol is a physiological effect due to the direct action of menthol on the nerve endings of the human body responsible for the detection of hot or cold and is not due to latent heat of evaporation. It is believed that the menthol acts as a direct stimulus on the cold receptors at the nerve endings which in turn stimulate the central nervous system.
Although menthol is well established as a physiological coolant its use in tobacco is circumscribed by its strong minty odour and its relative volatility. For example, it is well known that "mentholated" cigarettes deteriorate quite rapidly on storage.
A few other compounds have been reported in the technical literature as having an odour or flavour similar to methol and from time to time have been proposed as flavourants in tobacco. For example, Japanese Patent Publication No. 39-19627 reports that 3-hydroxymethyl p-menthane (menthyl carbinol) has a flavour closely resembling that of 1-menthol and suggests its use as a flavourant in tobacco. In Swiss Pat. No. 484,032 certain saccharide esters of menthol are proposed as additives to tobacco. Other compounds have been reported in the literature as having an odour and physiological cooling effect similar to menthol but without any specific recommendation for their use as additives in tobacco. For example, in French Pat. No. 1,572,332 N,N-Dimethyl 2-ethylbutanamide is reported having a minty odour and refreshing effect, and the minty odour of N,N-diethyl 2,2-dimethylpropanamide is referred to. A similar effect is reported for N,N-diethyl 2-ethylbutanamide in Berichte 39, 1223, (1906). A minty odour has also been reported for 2,4,6-trimethylheptan-4-ol and 2,4,6-trimethyl hept-2-en-4-ol in Parfums-Cosmetiques-Savons, May 1956, pp. 17-20. The cooling effect of menthol and other related terpene alcohols and their derivatives has also been studied and reported in Koryo, 95, (1970), pp. 39-43. 2,3-p-menthane diol has also been reported as having a sharp cooling taste (Beilstein, Handbuch der Organischen Chemie, fourth Ed. (1923) Vol. 6, p. 744).
Despite this knowledge of other compounds having an odour and flavour similar to that of menthol, menthol is still extensively used in tobacco notwithstanding the disadvantages mentioned above, namely its very strong odour and its relative volatility.